1. Field of the Invention
The present invention relates to a system for cutting work pieces by means of a laser beam. More particularly, it relates to a numerical control (hereinafter referred to as "NC") laser machine for cutting work pieces on the basis of a three-dimensional profile NC program.
2. Description of the Prior Art
Three-dimentional work pieces are machined on the basis of a three-dimensional profile NC program prepared in advance. However, it is very difficult to prepare three-dimensional profile NC programs directly from design drawings, etc. Even if the programs are accurately prepared, work pieces are not necessarily machined accurately in accordance with the design drawings because of various factors. A method tried in the past comprises putting a mark (for instance a trimming line) on a work piece, model, etc. to show the position to be machined, preparing a three-dimensional profile NC program by scanning the mark by means of an industrial robot, and then machining work pieces on the basis of the program. However, because the accuracy of scanning is low at present, programs thus prepared have large errors. Therefore, the application of scanning by an industrial robot is limited to spot welding, plasma cutting, etc. which do not require accuracy.